1. Field of the Invention
The present invention relates to a revolution detecting sensor such as a wheel speed sensor, or an engine revolution speed sensor of a motor vehicle.
2. Description of the Background Art
As disclosed in Japanese Patent Laying-Open No. 2000-180460, for example, a revolution detecting sensor constituting a wheel speed sensor includes a detecting portion detecting magnetic fluctuation, to convert to an electric signal. For the detecting portion, a configuration in which a magnet applying a bias magnetic field is provided behind a Hall IC, and a lead terminal from the Hall IC is connected to a circuit on a substrate is adopted, for example.
In a conventional revolution detecting sensor described above, the magnet applying the bias magnetic field to the Hall IC should be positioned behind the Hall IC with respect to a detection target. Therefore, the lead terminal from the Hall IC should go around (bypass) the magnet. Consequently, the lead terminal is connected to the circuit on the substrate in an elongated manner.
Recently, each motor vehicle manufacturer has pursued reduction of the number of components, the size and weight. Such a demand has been directed also to the wheel speed sensor. As the wheel speed sensor is made smaller, a volume for accommodating the component and a method of accommodating the same have increasingly been restricted. With regard to the wheel speed sensor as well, in order to arrange the component in a limited space, the lead terminal is subjected to a variety of bending (forming) processes for arrangement in many cases.
An example is shown in FIGS. 11A and 11B. Here, a Hall IC 2 is fit in front of a magnet holder 10. A lead terminal 5 from Hall IC 2 first suspends from Hall IC 2, and extends along the surface of a wall constituting the bottom of a magnet fit-in hole 12. Then, lead terminal 5 is bent toward the side of a substrate 1 at an end portion of the wall, and inserted for connection into a through hole 3a of a detecting circuit 3. Lead terminal 5 thus exhibits a shape of a cup. Hall IC 2 with cup-shaped lead terminal 5 is fabricated by bending straight lead terminal 5 of Hall IC 2 shown in FIG. 9A to the shape of a cup as shown in FIGS. 9B and 9C. Since lead terminal 5 is thin and susceptible to deformation, variation in processing is likely, or lead terminal 5 tends to be deformed again during transportation and connection. For example, lead terminal 5 may be deformed in such a manner as shown with a chain line in FIGS. 10A and 10B.
As described above, when lead terminal 5 is attached to holder 10 and substrate 1 while it is not in a prescribed shape, as shown in FIGS. 11A and 11B, a tip end of lead terminal 5 is bent, without properly introduced into through hole 3a of detecting circuit 3 (FIG. 11A). In addition, if insertion of lead terminal 5 is forcibly attempted, lead terminal 5 may depart from the through hole, which will adversely affect a quality in a mold portion of Hall IC 2 (FIG. 11B). Such bending and departing will result in poor connection and a defect. Moreover, workability has been low, because such a defect should be corrected, that is, connected again, for example.